Experimental and simulation studies on focused ultrasound triggered drug delivery.

To improve drug delivery efficiency in cancer therapy, many researchers have recently concentrated on drug delivery systems that use anticancer drug loaded micro- or nanoparticles. In addition, induction methods, such as ultrasound, magnetic field, and infrared light, have been considered as active induction methods for drug delivery. Among these, focused ultrasound has been regarded as a promising candidate for the active induction method of drug delivery system because it can penetrate a deep site in soft tissue, and its energy can be focused on the targeted lesion. In this research, we employed focused ultrasound as an active induction method. For an anticancer drug loaded microparticles, we fabricated poly-lactic-co-glycolic acid docetaxel (PLGA-DTX) nanoparticle encapsulated alginate microbeads using the single-emulsion technique and the aeration method. To select the appropriate operating parameter for the focused ultrasound, we measured the pressure and temperature induced by the focused ultrasound at the focal area using a needle-type hydrophone and a digital thermal detector, respectively. Additionally, we conducted a simulation of focused ultrasound using COMSOL Multiphysics 4.3a. The experimental measurement results were compared with the simulation results. In addition, the drug release rates of the PLGA-DTX-encapsulated alginate microbeads induced by the focused ultrasound were tested. Through these experiments, we determined that the appropriate focused ultrasound parameter was peak pressure of 1 MPa, 10 cycle/burst, and burst period of 20 μSec. Finally, we performed the cell cytotoxicity and drug uptake test with focused ultrasound induction and found that the antitumor effect and drug uptake efficiency were significantly enhanced by the focused ultrasound induction. Thus, we confirmed that focused ultrasound can be an effective induction method for an anticancer drug delivery system.